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MPLS Source Label. draft-chen-mpls-source-label-01. Mach Chen Xiaohu Xu Zhenbin Li Luyuan Fang IETF88 MPLS Nov . 2013 Vancouver. Problem Statement and Motivation. No information about source encoded in MPLS label stack
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MPLS Source Label draft-chen-mpls-source-label-01 Mach Chen Xiaohu Xu Zhenbin Li Luyuan Fang IETF88 MPLS Nov. 2013 Vancouver
Problem Statement and Motivation • No information about source encoded in MPLS label stack • A MPLS label identifies a FEC and assumes the destination address semantic • Intermediate and egress LSRs can NOT tell from which LSR a packet is sent. Especially for: • MP2P and MP2MP LSP (e.g., LDP based LSP, L3VPN, etc. ) • Segment Routing based LSP (without per-flow state) • Source identification is critical for some applications • Performance Measurement, Traffic Matrix Collection • Segment Routing - “… preserving information on the topological and service journey of a packet (e.g. the ingress to the domain for accounting/billing purpose).”
Solutions • MPLS Source Label (SL) • Designed to identify ingress LSR of an LSP, could be: • Global label, or • Locally significant label • Similar to BGP VPLS Label Block (RFC 4761) • Source Label Indicator (SLI) • A special purpose label (TBD) • Placed immediately before the SL • Indicate the next label is a SL … LSP Label SLI SL … MPLS label stack
Use Cases (1) • Performance Measurement (E.g., Packet Loss, throughput) • Source identification is the precondition of PM • To help the Egress or intermediate LSRs for counting LSP Label SLI PE1 Insert SL1 SL1 PE3 LSP Label PE2 Insert SL2 SLI SL2
Use Cases (2) • Traffic Matrix Collection and Steering • When Link C-D reaching its threshold • Collect the traffic matrix over Link C-D ( at either node C or D): • Which flows are from node A and B? (Based on Source Label) • What’s the volume of each flow? • Then determine which flows should be moved onto other paths Controller Controller E E A A Ingress Steering Report Egress G G B B Ingress C D D F C F
Compatibility Consideration • Egress LSR • Source Label Capability (SLC) negotiation: Egress signal to Ingress LSR it is able to process SL • Based on the SLC, ingress LSR can choose whether or not to insert SL into the stack • Transit LSR • There is no change in forwarding behavior for transit LSRs. But if a transit LSR can recognize the SLI, it may use the SL to collect traffic throughput and/or measure the performance of the LSP. • So, there is no compatibility issue.
Next Steps • Would like to solicit more comments and update the draft. • WG adoption?